In the technique of mass stamping of metal pieces, two large families of stamping devices are now known:
devices called "following tools" for which the metal strips itself supports the stamped products made in this strip. In these devices, feeding of the metal strip is performed along the axis of the machine, and it is called longitudinal feeding. These devices use a traditional press, on which the following tools are mounted;
"transfer presses" in which the metal pieces to be processed are first totally detached from the metal strip which feeds the machine, and transferred from one stamping station to the next in this machine by means of transfer rods which are totally integrated in this machine. On these devices, feeding by the metal strip is necessarily crosswise, if only because evacuation of the scraps at the moment of cutting the pieces from the strip obviously cannot be performed in the axis of the machine, but rather perpendicular to this axis.
Use of a transfer press is essential for the performance of certain stamping works, which it is impossible to perform by a standard press equipped with following tools.
The transfer presses have the drawback of being relatively complex and consequently of rather high cost relative to presses with following tools. Further, the necessity of feeding each press crosswise is very disadvantageous for installation in shops, since it is necessary to provide sufficient space there to allow this crosswise feeding. Finally, these presses are unique, and of course specific for the stamping work with automatic transfer from one station to the next: they cannot be suitable for work with following tools, which are often preferred because they are more profitable and more economic, or other press works.
A press with longitudinal feeding is known from U.S. Pat. No. 3,969,918. This press is of the type comprising means for cutting, from a longitudinally fed strip, a blank to be stamped, these cutting means consisting of a stationary lower punch carried by the press table and a vertically movable upper die, normally located above the punch and intended to be moved in the direction of the punch by a mobile press slide, means for cutting off the end scrap from the strip consisting of shears exhibiting a stationary blade and a mobile blade, a device for transfer of a cut, prestamped or stamped blank, from the station it occupies to the next station and means to lift each cut blank to the level of the transfer device.
In this press, the means for cutting the blanks and those for cutting the scraps are separate and independent of one another.
Further, the device for transfer of the blanks is placed at a level located just above the upper face of the punch and, consequently, below the high rest position of the die. Consequently, after having cut a blank, during its descending travel, the die must be lifted above this blank which, so that its edges will not be deformed during the ascending travel of the die, should be kept perfecting applied, by its peripheral edge, against the punch, which increases the wear of the cutting edges of the die and especially complicates its shape since it must comprise an annular inside pusher of the same outside perimeter as the punch, a pusher inside which means for lifting the blanks should circulate.
Finally, in this press, the die, the annular pusher and the means for lifting the blanks constitute an independent subassembly of the punch which is intended to be fastened to a mobile press slide while the mobile blade of the shears constituting the means for cutting the scrap is carried by a spring-mounted strap and carried by the lower base plate of the tool.
It can easily be seen that not only is this tool necessarily very complex, but, further, any change in the shape of the blank requires long, costly operations of disassembly of the old tool and assembly and adjustment of the new one.